The design of modern television receivers increasingly involves the use of digitally controlled chips (i.e., integrated circuits) for control of many different functions, such as, picture processing, picture-in picture (PIP) processing, and audio processing. These chips are connected to a controller (which may be a microprocessor, a microcomputer, or a dedicated control IC) via a communications bus. The controller is responsible for writing control parameters to the chips and reading status information from the chips. This process results in a large amount of data being communicated between the controller and its peripheral chips because each of the chips contain programmable registers which must be written to, or read from, to on a periodic basis. Unfortunately, the data stored in these registers are subject to corruption caused by a variety of sources, such as, electrostatic discharge (ESD), radio frequency interference (RFI), high voltage arcing within the picture tube (kine arcs), power supply spikes, etc. It is possible that any of these sources of corruption could cause the instrument to fail to respond to a command (i.e., lock-up) if the controller were waiting for a chip to respond to a request for data. Another result of such corruption is the production of invalid data which is likely to cause unpredictable behavior.
In the computer art it is well-known to use a circuit commonly-known as a watch-dog timer to prevent a specific kind of lock-up, that is, a lock-up in which the microcomputer itself is no longer following its own program instructions due to an incorrect count in its program instruction pointer. A watch-dog timer is a hardware timer with a preset period. If the microcomputer does not return to reset the watch-dog timer before the preset period expires, then an internal reset is initiated to restart the microcomputer at a predetermined program location.
It is also notoriously well-known that many chips include a reset pin for applying a external pulse to force the chips to a known state. Unfortunately, today's chips are quite complex and require many pins (i.e., terminals) for the accomplishment of their particular function. In such chips, pins are at a premium and some manufacturers are reluctant to dedicate a pin to a reset function.
In the automotive electronics art, it is known to monitor various automotive processes and store error codes indicative of discovered problems, as a diagnostic aid to a repair mechanic.